The US map isn't tight enough in some of our 4-player games here (depends on the group, so far) - so I've avoided playing the Ruhr, since presumably that would exacerbate this problem. (I've been thinking about slicing a couple of cities off the US map sometime, or else playing a subsection of the Ruhr.) Anyone else have similar experiences?

Nope. The extreme amount of mountains makes the game very tight. Maybe you just had the cubes set up in an "easy" distribution. It happens sometimes. The same map with the same number of players might be brutal one game and easy the next, depending on the cube draw.